I recently faced a situation where customer requested to change the hostname of backend SQL DB Virtual Machine . I followed the below procedure

• Take the Backup of vCenter Database
• Shutdown vCenter Services
• Shutdown SQL Services on SQL Server.
• Rename the SQL Server Hostname to desired hostname.
• Restart SQL Server.
• Validate the SQL services are up and running after the restart.
• Connect to SQL Management Studio to validate the connection to DB.
• On the vCenter Server open ODBC Connections and reconfigure the current odbc connection to point to new hostname.
• Then edit SQL Server Hostname in the vcdb.properties file which is located at:
  • For vCenter Server 5.5 and earlier:
    • Windows 2008 – C:\ProgramData\VMware\VMware VirtualCenter
    • Other Windows versions – C:\Documents and Settings\All Users\Application Data\VMware\VMware VirtualCenter\

  • For vCenter Server 6.0:
    • C:\ProgramData\VMware\vCenterServer\cfg\vmware-vpx
• Start the vCenter Services and you are ready to ROCK N ROLL 🙂

More information can be found on the below VMware KB

https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=7960893